Aug 12, 2014
HRS observations of rapidly oscillating (roAp) stars
Waves inside some stars make their light to change periodically. These changes are called pulsations. By breaking down this variable light into colours, thereby forming a spectrum of a star we can learn many important aspects of a star. Our project studies the spectra of stars with surface temperature of between 6000 and 10000 degrees in order to study how the different elements of these stars are distributed in different layers of the surface layers of the star. This will ultimately allow us to learn in detail what role the magnetic field in these stars affect their structures.
Aug 11, 2014
Rapid oscillations in spectroscopically selected chemically peculiar stars
In this program we study chemically peculiar Ap stars which show overabundances of chemical elements like chromium and strontium. These stars also have very large overabundances of rare earth elements including praseodimium, neodimium, europium. Ap stars rotate more slow then normal stars with the same spectral type.These stars also have strong magnetic fields and some of them show pulsations with very short period.
A Precision Test of Low Mass Stellar Evolution Models
Jul 31, 2014
Why does it flare? The eccentric, heavyweight neutron star in IGR J17544-2619
I am studying a binary star, in which one of the massive companions has exploded, leaving behind a “neutron star”. This neutron star orbits the surviving companion every five days. Theory says that this orbit must be circular, but X-ray observations suggest that it should be eccentric (flattened). The aim of these observations is to figure out the real shape of the orbit.
Jul 30, 2014
Ionized Gas Kinematics for Obscured Quasars with Molecular Gas Measurements
We are studying the gas a galaxy that contains a powerful, “hidden” supermassive black hole at its center. The radiation from this black hole lights up the gas in the galaxy, much like a fluorescent lamp, and we are using SALT to study this fluorescent light. The light we observe with SALT will tell us about how the gas is rotating and moving around inside the galaxy, and help us determine what effects the black hole’s radiation might have on how the galaxy grows and forms stars over the history of the Universe.
Jul 28, 2014
Longevity of Dark Matter Substructures in Abell 3827
Our Universe matter content today is dominated by Dark Matter.If it is called dark matter, it is because we don’t know much about its nature.Abell 3827 is an exceptional massive galaxy cluster not too far from us. Its core is formed by four massive galaxies, that are still in the process of merging together.This configuration is really rare and makes Abell 3827 a primary target to study the evolution of dark matter.With these observations, we will be able to see where the stars (luminous matter) and the dark matter are situated with a really high accuracy.This is mandatory to understand the history of this rare and exceptional galaxy cluster, but not only ! By looking at the location of the stars compared to the dark matter, we will be able to derive clues on the properties of dark matter particles.
Jul 22, 2014
Constraining dark matter in the centres of clusters
We are using SALT to observe the dominant galaxies in the centres of clusters to learn about the dark matter in the cluster. Dark matter can not be directly observed, but observations of the random motions of stars in these galaxies can be used to describe the dark matter in the cluster if the data is combined with other observations from the Hubble Space Telescope and X-ray observatories.
Jul 21, 2014
Spin-up of the O Companions in WR+O binaries
We propose to measure the spin rates (vsini) of 16 O stars in WR + O binaries. Theory predicts that the mass transfer from their WR companions will have boosted many to nearly breakup velocity. Only two systems are well studied (V444 Cyg and HD 186943); both are very rapidly rotating. The observed vsini distribution will be critical to constrain mass transfer theory, and binary massive star evolution.
Jul 19, 2014
Fundamental Properties of Peculiar Hot Subdwarfs
Stars approaching the end of their lives expand and, in many cases, exchange material with close companions. This has a radical effect on their evolutionand surface composition, producing a zoo of rare but highly exotic stars. By exploring the propertiesof thes pathological cases, we are endeavouring to understand the ways in which stars exhange matter and evolve towardstheir final fate as white dwarfs or supernovae. The stars in this programme are perfect examples — all of them have completelylost their surface hydogen, for reasons still to be explained. These observations will tell us about the abundances of otherelements — previously we have discovered huge overabundances of exotic species such as lead and zirconium.
Jul 15, 2014
Calibrating RINGS: RSS Imaging and Spectroscopy Nearby Galaxy Survey (phase II)
We will measure the orbital speeds of hydrogen gas cloudsin nearby galaxies like our own Milky Way, and we will use them to derive the total mass distribution of each system. By comparing this mass to those of the gas and the stars in each system, we can map its dark matter content. Our main scientific goal is to compare this dark matter content to theoretical models developed from computer simulations of the evolution of the Universe: are our observationsconsistent with predictions from the standard cosmological model input into the simulations, or is our understanding of cosmology and/or galaxy formation incomplete?